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최낙선,강민성,김광해,고대우,Choi, Nag-Sun,Kang, Min-Seong,Kim, Kwang-Hae,Koh, Dae-Woo 한국시스템엔지니어링학회 2009 시스템엔지니어링학술지 Vol.5 No.2
KC-100(KAI Civil Aircraft, Small Series) aircraft is 4 seats general aviation aircraft with single piston engine which is developing under FAA part 23 category by Korea Aerospace Industries(KAI) and will be a shadow program for civil aircraft safety infrastructure improvement. This aircraft will be the first civil aircraft developed in Korea meeting the Korean regulatory KAS Part 23 requirements. Type certification for KC-100 aircraft was applied at the second half of this year. The type certificate is expected to be issued after 3 years of design, prototype manufacturing, ground and flight tests. In this paper the system engineering process for civil aircraft was first reviewed. Next, the differences and similarities in the system development between military and civil aircraft were systematically examined using experiences for KAI military aircraft development program.
주파수 영역에서 연속체 민감도법을 이용한 유전체 저대역 필터 최적 설계
최낙선(Nak-Sun Choi),정기우(Gi-Woo Jeung),김남경(Nam-Kyung Kim),변진규(Jin-Kyu Byun),김동훈(Dong-Hun Kim) 대한전기학회 2010 전기학회논문지 Vol.59 No.8
This paper presents a new methodology for designing a dielectric waveguide filter with the cutoff frequency of 2.4 ㎓ based on the continuum design sensitivity analysis. An analytical sensitivity formula is derived in frequency domain and then unified program architecture applicable to the optimal design of high-frequency devices is proposed. A three-dimensional dielectric resonator used in waveguide filters has been tested to illustrate the validity of the proposed method.
전자파의 집중도를 이용한 바이모달 트램의 전자파 차폐 성능 분석
최낙선(Nak-Sun Choi),정기우(Gi-Woo Jeung),김남경(Nam-Kyung Kim),송명곤(Myung Kon Song),이강원(Kang-Won Lee),목재균(Jai-Kyun Mok),김동훈(Dong-Hun Kim) 대한전기학회 2011 전기학회논문지 Vol.60 No.7
In this paper, the electromagnetic shielding performance of a BiMODAL Tram is investigated by means of an electromagnetic analysis tool, called HFSS. For the purposed of doing this, first, three-dimensional finite element modeling for the tram including electronic devices and engine room is carried out. Then, for quantitatively assessing the electromagnetic shielding performance of the tram’s body, concentration indexes for electric field magnitude and time-average stored electric energy are introduced. From numerical results, it is inferred that the tram’s body can protect the electronic devices and engine room against external electromagnetic waves from 30 ㎒ to 100 ㎒.
비촉지성 갑상선 결절의 진단에서 초음파 유도하 세침검사법의 임상적 가치
최낙선(Nak Seon Choi),윤정한(Jung Han Yoon),제갈영종(Young Jong Jaegal) 대한두경부종양학회 1999 대한두경부 종양학회지 Vol.15 No.2
Objectives: Fine needle aspiration cytology(FNAC) is a well established preoperative diagnostic procedure in the thyroid nodules. However, diagnostic accuracy of FNAC varies according to the size and the structural characteristics of thyroid nodule. We performed the ultrasound guided FNAC(US-guided FNAC) for impalpable thyroid nodule, and estimated the sampling accuracy rate through a comparison study between the cytologic diagnosis and the final histologic diagnosis of the postoperative specimens in order to determine clinical efficacy of the US-guided FNAC. Materials and Methods: We evaluated 117 patients underwent US-guided FNAC from January 1997 to December 1998. These patients had 129 thyroid nodules to need cytologic examination. Whereas the nodules were so no graphically classified into cystic, solid, and mixed type according to echo pattern, the aspirated thyroid specimens were classified into benign, malignant, suspicious, and insufficient. Results: Positive sampling for diagnositc examination was achieved in 75 nodules(58.1%), and US-guided FNAC in our study showed the accuracy rate of 95.2%, false positivity rate of 0%, and false negativity rate of 5.5%. Conclusions: US-guided FNAC is a powerful techniques for evaluating cytologic characterics and allowing a reliable diagnositc result in the impalpable thyroid nodule. However, the experienced technique is recommanded in order to obtain the sufficient samples for reliable results.
최낙선(Nak-Sun Choi),정기우(Gi-Woo Jeung),김동욱(Dong-Wook Kim),양창섭(Chang-Seop Yang),정현주(Hyun-Ju Jun),김동훈(Dong-Hun Kim) 대한전기학회 2012 전기학회논문지 Vol.61 No.10
This paper analyzes re-degaussing performances of various breakdown conditions of degaussing coils in a ship to reduce underwater magnetic field anomaly due to the hull magnetization induced under the Earth’s magnetic field. To achieve this, first, it is implemented to optimize degaussing coil currents by a magnetomotive force sensitivity formula combined with the coil effects. The re-degaussing processes are then executed when a breakdown occurs in degaussing coils, one by one. Finally, the re-degaussing performances are examined with the results of normal degaussing and coil breakdown conditions.
샘플링 기반 민감도를 이용한 국부 유도 가열용 코일의 최적 설계
최낙선(Nak-Sun Choi),김동욱(Dong-Wook Kim),김동훈(Dong-Hun Kim) 한국자기학회 2013 韓國磁氣學會誌 Vol.23 No.3
This paper proposes a sampling-based sensitivity method for dealing with electromagnetic coupled design problems effectively. The black-box modeling technique is basically applied to obtain an optimum regardless of how strong the electromagnetic, thermal and structural analyses are coupled with each other. To achieve this, Kriging surrogate models are produced in a hyper-cubic local window with the center of a current design point. Then design sensitivity values are extracted from the differentiation of basis functions which consist of the models. The proposed method falls under a hybrid optimization method which takes advantages of the sampling-based and the sensitivity-based methods. Owing to the aforementioned feature, the method can be applied even to electromagnetic problems of which the material properties are strongly coupled with thermal or structural outputs. To examine the accuracy and validity of the proposed method, a strongly nonlinear mathematical example and a coil design problem for local induction heating are tested.
김광해,최낙선,고대우,Kim, Kwang Hae,Choi, Nag Sun,Koh, Dae Woo 한국시스템엔지니어링학회 2010 시스템엔지니어링학술지 Vol.6 No.1
The Test and Evaluation (T&E) process is an integral part of the Systems Engineering Process. The purpose of Test and Evaluation (T&E) in a system development is to identify the areas of risk to be reduced or eliminated. In this study, when develop aircraft of Civil Aviation with development experience of Military Aircraft, it is that establish Test and Evaluation process. Test and Evaluation for KC-100 small aircraft development can divide to certification test and development test. Certification test is proved compliance about Korea Airworthiness standard (KAS Part 23), through Development Test verify required performance of aircraft. These Test and Evaluation Process is more efficient and optimized.